Hugged your ground recently? Or when 120VAC turns to 240VAC!

[Rick Sutton]

Things got really strange at the studio today. The AC feed just wouldn't stay as stable as it always is and I eventually shut everything down and started investigating. I couldn't figure out why the voltage would be fine for several hours and then spike up 10 to 15 volts high for a second or two and at the same instant dip on another circuit. Had a electrician friend come over and he measured a few things and proclaimed that the problem was coming in from the electric company (PG&E) and I'd better get them out here quick. OK, PG&E comes out, takes a bunch of readings and of course nothing is screwing up so after convincing them that I'm not a total whacko and I've taken readings up to 142 volts inside for quick flashes the guy says he'll go climb the pole and report back. 15 minutes later the guy is at my door and the first thing out of his mouth is " You must have one hell of a good ground in this building 'cause our neutral is completely disconnected."
To those of you unfamiliar with US 120 volt wiring and the neutral wire.....if the neutral gets compromised you can have 240 volts across what is supposed to be a 120 volt line.....a very ugly situation.
Anyway, back to grounds. When we built this control room on to a very old bulding 31 years ago the one thing that we really went overboard on was a real ground system that is centered on a very large copper stake that is buried in the ground right outside the CR. With the addition of more gear over the years feeders have been added to the ground using #2 wire and heavy buss bars. The electrical drop is tied securely to this ground. Probably all standard code now but at the time we were in an unincorporated area and we did way more than necessary.......and today really proved the worth of the excercise. The entire electrical system with all the juice being pulled was using our copper rod as the only ground reference. WAY too close to disaster! To those of you who think PG&E would have payed for the damage...dream on. They'd pay pennies on the dollar and I'd have been stuck with a huge ordeal to get everything repaired.

Lest anyone might think I'm bragging about having any real part in averting this awful disaster let me tell you that I'm the guy that once destroyed 10 brand new Denon 3 head, very expensive, cassette decks with the single touch of a clip lead faster than you can say POOF! Today I got lucky. I'm still kinda shaky and nervous from how close it was. This almost ended up in another current thread, the one that asks "What gear have you blown up this month?."


Just thought I'd share this and ask, Have you hugged your ground recently? Do you even know if you have a good ground? Might be worth checking out.
Cheers, Rick

[max cooper]

Coincidence? I went to help a friend with his hifi the other day. He was getting noise and humming.

I brought new cables because his were in kinda bad shape. So I put my hand on top of the receiver to brace it so I could plug the first audio input in (from the cable box) and as soon as I picked up the cable, I got shocked so bad it almost knocked me on my a$$.

And yeah, we were reading 140-some-odd volts here too.

I checked the polarity of the AC and it was fine, but when I checked the ground, the tester said there was none.

The power company is coming out. I think the lack of ground could be due to the drought conditions.

[joelpatterson]

If there's no ground... then where did all the dirt come from?

[Rick Sutton]

Originally Posted by max cooper

I think the lack of ground could be due to the drought conditions.

Yeah Max, I've been having indications that something was not right here for several weeks (very slight fluctuations) and three days ago I put a meter on it and each day the changes got bigger until late Monday eve when it started to get scary.
We figure that the neutral wire may have been off here for quite a while, possibly since the last winter storm, and with the drying of the ground over the summer my ground became less able to carry all the load. After PG&E left yesterday I installed a new branch of the landscape drip system to water my studio ground area.......just in case.

[littlelabs]

Years ago when I lived in an old apartment next to the Whiskey au go go, I had pulled a plate off the wall and wanted to tie something in. I thought power was off on the breakers for that box, and I started to loosen one of those wire nut plastic cover doo hickeys, and my lights in the house went sooo bright I thought for a second I was you know, going up stairs to the harps and shit. I got a grip and put the wire nut back on and the lights came back to good old earth, amazingly nothing did blow up. I was lucky, as were you.

[2leod]

Originally Posted by max cooper

I think the lack of ground could be due to the drought conditions.

You know, I was just thinking the same thing on Monday. Had a couple of friends over jamming in the studio and I noticed that my amp was buzzing more than normal. After checking the usual suspects I discovered the noise was less when sat on a chair with my feet up, not touching the cement slab with my damp socks (ok, now you all know I have sweaty feet) and went away when I touched the strings. It's been an exceptionally dry summer for us and the place where the ground rod is doesn't ever get watered - it made me nervous that I could be making a better path to ground than the rod, so shoes on for the rest of the night.

[Rick Sutton]

Originally Posted by 2leod

- it made me nervous that I could be making a better path to ground than the rod

Ever hear the statement "He's such a level headed, well GROUNDED guy".?
In our field we don't want to be the most GROUNDED thing around when the juice is having a hard time finding it's own ground. That when your level head turns into a frizzzz hairdoo. YEOOOWWWW!

[Dan Kennedy]

Had a similar thing happen, but had to fight with the morons at NSP for a week before they came back and finally fixed it.

The pole pig had a swinging neutral, so down at the building it was all over, load dependant. They came out a couple of times, couldn't find anything, 'cause it came and went, seemingly weather related, and finally told me I had to get a master electrician out there before they'd even listen to me.

Had the guy booked, but luckily, sorta, a neighbor on the same feed came home from vacation, turned on his TV, which promptly blew up and got on the horn, screaming bloody murder.

[max cooper]

So can anyone comment on what to do when the cable and the AC have different ground potentials?

Lots of people connect their cable to stuff that's connected to AC, like cable modems to computers, or cable-box audio to the hifi.

And yes, always rubber soles when messing with elec. devices on concrete. My loft has concrete floors and I've been jolted making toast while barefoot.

Remember how Oddjob met his demise?

[2leod]

Originally Posted by Rick Sutton

That's when your level head turns into a frizzzz hairdoo. YEOOOWWWW!

Me after the smoke clears...

[dbbubba]

If your cable service or phone service have a different GND then you WILL get a lo0p if it is introduced into the audio system.
I worked for a studio that had a nice SSL, but there was hum in the control room it lived in.
While re-configuring some stuff for a ADR sessioin I discovered that when I un-plugged a VHS deck in the hum would appear.
The VHS deck was hooked up to a TV moitor in the soffit and that TV monitor was also hooked up to the SSL computer to show recall.
The cable was hooked into the VHS deck, so there was the loop!

We remedied it by un-hooking the cable's sheild at the input to the VCR.
The sheild only needs to be tied at one eendd to do it's job 100%.

We have a large 200 amp distro panel we use on some shows that is not in a box.
It is just a painted metal load center.
There is definitely a GND loop if it is lying on concrete and it is worse outdoors.
In fact, it doesn't even meet code although it is considered a temporary system.
On concrete we have at least 2x4s to lie it on to de-couple it.

Danny Brown

[cornutt]

Some years ago, I worked in a spacecraft integration facility in Florida. One weekend the building was hit by lightning. Next Monday, the problems started showing up. The big one was that some high-speed data networking ports, implemented with totally custom and flight-qualified hardware, on equipment inside the spacecraft itself were blown. Several million dollars' worth of damage.

The building had an extensive ground system installed, with single-point grounding to a point that connected to a mesh of ground rods every twenty feet or so all around the building. But that had been ten years since it was installed, and when they checked the ground system, they found that the salt water in the soil had eaten all the rods away.

[sedohr]

Originally Posted by max cooper

So can anyone comment on what to do when the cable and the AC have different ground potentials?

Lots of people connect their cable to stuff that's connected to AC, like cable modems to computers, or cable-box audio to the hifi.

And yes, always rubber soles when messing with elec. devices on concrete. My loft has concrete floors and I've been jolted making toast while barefoot.

Remember how Oddjob met his demise?

Ah, good old oddjob. How was it again, something about electricity...He got grounded..Shocking!



Kalli

[digitalM]

Alright guys;

[tINY]

Good ground! Probably a good ballance between the legs too....

You still out by yourself, Rick? Or have rows of boxes grown up around you?



-tINY

[Rick Sutton]

Originally Posted by tINY

Good ground! Probably a good ballance between the legs too....

You still out by yourself, Rick? Or have rows of boxes grown up around you?



-tINY

yeah tINY, We had the two legs running with a differential of about 2 volts between them but towards the last few days when one leg would swing high the other would drop low. It got pretty goofy. In my original post I condensed the timeline as it actually took 4 days and three visits by PG&E and one by an electrician before we finally got it fixed and I felt comfortable turning the control room equipment back on.

As to my area, it incorporated into a city about 15 years ago and houses have definitely doubled or tripled, I'm on an acre with the studio and I don't think it will be much longer 'til we'll be squeezed out. The acre will probably go from one little recording studio/house (we moved out twenty years ago) to 4-6 townhouses. I might move a down-scaled studio to my current house on 2 acres outside of town or I might just called it a day. Time will tell.